JP3771967B2 - Axial flow turbine - Google Patents

Description

【００５９】
この関係式の範囲は、湾状曲線ＣＬから噴出する蒸気の押圧作用力を、動翼１３の遠心力の影響を加味して若干セーブさせ、ノズルチップ部半径位置Ｒｔ側が高流量になることを回避するために、試行錯誤を繰り返して算出した実験結果である。
【００６０】
上述の関係式は、蒸気の押圧作用力により、ノズルチップ部半径位置Ｒｔ側が高流量になることを回避させる最も好ましい適用範囲である。
【００６１】
図５は、座標βにタービン軸１４の回転中心Ｏを通るラジアル線Ｘｒに対し、ノズル１２の後縁線１９のうち、直線ＳＬの傾斜角度値および湾状曲線ＣＬの傾斜角度値を、また座標Ｒにタービン軸１４の回転中心Ｏを通り放射状に延びる半径方向距離値をそれぞれ示したものである。また、図６は、図５に示す直線ＳＬおよび湾状曲線ＣＬの傾斜角度変化値に対応させた蒸気の流出角を示すものである。座標αは、図５の直線ＳＬおよび湾状曲線ＣＬの傾斜角変化値に対応する蒸気の流出角変化値を示す。
【００６２】
これら図５および図６において、直線ＳＬの傾斜角βは、ノズルルート部半径位置ＲｒからノズルＰ．Ｃ．Ｄ．半径位置Ｒ_PCD に向って低下し、また蒸気流出角αはノズルルート部半径位置ＲｒからノズルＰ．Ｃ．Ｄ．半径位置Ｒ_PCD に向って増加しており、これらのデータから後縁線１９の直線ＳＬで噴出する蒸気の押圧作用力は、ノズルルート部半径位置Ｒｒ側からノズルＰ．Ｃ．Ｄ．半径位置Ｒ_PCD 側に進むに連れ、その方向性を変えている。したがって、後縁線１９の直線ＳＬから噴出する蒸気の押圧作用力は、ノズルルート部半径位置Ｒｒ側においても作用しているので、ノズルルート部半径位置Ｒｒに蒸気が流れ、その周辺での低流量域を回避することができる。
【００６３】
一方、湾状曲線ＣＬは、図５および図６に示すように、ノズルＰ．Ｃ．Ｄ．半径位置Ｒ_PCD からノズルチップ部半径位置Ｒｔにかけて傾斜角βを急激に低下させる一方、ノズルチップ部半径位置Ｒｔの傾斜角βｔの絶対値がノズルルート部半径位置Ｒｒの傾斜角βｒよりも小さくなっており、また傾斜角βの変化値に対応させた蒸気の流出角αの変化値もノズルＰ．Ｃ．Ｄ．半径位置Ｒ_PCD からノズルチップ部半径位置Ｒｔの範囲内のノズル半径位置Ｒ₀ におけるラジアル線Ｘｒに対する傾斜角ゼロ値でピーク値を採り、以後、ノズルチップ部半径位置Ｒｔで流出角αｔは下っている。
【００６４】
上述のデータから理解できるように、湾状曲線ＣＬから噴出する蒸気の押圧作用力は、ノズル半径位置Ｒ_０で最大になっている。ノズル半径位置Ｒ _０ で押圧作用力を最大にしたのは、動翼１３の遠心力の影響によりノズルチップ部半径位置Ｒｔ側が高流量域になることを回避するためである。
【００６５】
図７は、図５および図６に示す直線ＳＬおよび湾状曲線ＣＬの傾斜角βの変化値、蒸気の流出角αの変化値に基づいて段落１１を通過する蒸気の流線Ｓをプロットしたものであり、また、図８は、図７の流線Ｓに基づいてノズルルート部半径位置Ｒｒからノズルチップ部半径位置Ｒｔまでの蒸気流量Ｑの分布を作成したものである。
【００６６】
図７および図８から理解できるように、蒸気は、ノズル１２の後縁線１９を噴出するとき、ノズルルート部半径位置Ｒｒからノズルチップ部半径位置Ｒｔに対する全域で均一化されている。
【００６７】
このように、本発明に係る軸流タービンでは、ノズル１２の後縁線１９を傾斜状の直線と湾状曲線とに区分けし、ノズルルート部半径位置Ｒｒに押圧作用力を与えているので、ノズルルート部半径位置Ｒｒ側の低流量域を回避することができる。また、ノズルチップ部半径位置Ｒｔに与えられる押圧作用力をセーブさせているので、ノズルチップ部半径位置Ｒｔ側の高流量域を回避することができる。
【００６８】
図９および図１０は、ともに本発明に係る軸流タービンの第１実施例を示す概略図である。なお、図２および図３の構成部品と同一構成部分には同一符号を付す。
【００６９】
本実施例は、図９に示すように、ノズル１２の後縁線１９を、直線ＳＬと湾状曲線ＣＬとに区分けした点で、図２および図３に示す実施形態と基本的に軌を一にしているが、湾状曲線ＣＬの形状を異ならしめている。
【００７０】
湾状曲線ＣＬは、図１０に示すように、タービン軸１４の回転中心Ｏを通るラジアル線Ｘｒに対し、傾斜角βｒを持たせ、ノズルルート部半径位置ＲｒからノズルＰ．Ｃ．Ｄ．半径位置Ｒ_PCD に向って放射状に延びる直線ＳＬに接続されるが、その曲率は変形長円形の曲率が利用されている。変形長円形の曲率は、ノズル半径位置Ｒ₀ でラジアル線Ｘｒに対し傾斜角をゼロにし、ノズルチップ部半径位置Ｒｔで高流量域を回避できる範囲に設定されている。
【００７１】
このように、本実施例は、ノズル１２の後縁線１９を、ノズルルート部半径位置Ｒｒ側が低流量域になることを回避し、またノズルチップ部半径位置Ｒｔ側が高流量域になることを回避するための直線ＳＬと湾状曲線ＣＬとに区分けしているので、図２および図３に示す実施形態と同様に、ノズル１２の後縁線１９から噴出する蒸気の流量分布を均一化させることができる。
【００７２】
【発明の効果】
以上説明したように、本発明に係る軸流タービンは、ノズルの後縁線を、ノズルルート部半径位置からノズルＰ．Ｃ．Ｄ半径位置に亘って傾斜状の直線に形成し、ノズルＰ．Ｃ．Ｄ．半径位置からノズルチップ部半径位置に亘って湾状曲線にしたので、ノズルルート部半径位置側、ノズルチップ部半径位置側ともに、蒸気を適正な流量として流すことができる。
【００７３】
また、本発明に係る軸流タービンは、湾状曲線の曲率を、（Ｒｔ−Ｒｒ）／２＜Ｒ＜１０（Ｒｔ−Ｒｒ）の範囲に設定してあるので、ノズルＰ．Ｃ．Ｄ．半径位置側からノズルチップ部半径位置側までを均一な蒸気流量として流すことができる。
【００７４】
また、本発明に係る軸流タービンは、湾状曲線から噴出する蒸気の押圧作用力のピーク値を、ノズルＰ．Ｃ．Ｄ．半径位置からノズルチップ部半径位置の範囲内に設定したので、動翼の遠心力の影響を受けても適正流量としてノズルチップ部半径位置側に蒸気を流すことができる。
【００７５】
したがって、本発明に係る軸流タービンでは、ノズルの後縁線から噴出する蒸気の流量分布を、ノズルルート部半径位置からノズルチップ部半径位置の全域に亘って均一化でき、翼効率の高いノズルを実現でき、軸流タービンの翼効率の向上により、発電効率を飛躍的に向上させることができる。
【図面の簡単な説明】
【図１】本発明に係る軸流タービンの段落の一部を示す概略断面図。
【図２】図１のＡ−Ａ矢視方向から見たノズルの概略斜視図。
【図３】本発明に係る軸流タービンのノズルの後縁線側から見た概略断面図。
【図４】本発明に係るノズルの形状を示す模式図。
【図５】タービン軸の回転中心を通る基準線（ラジアル線）に対するノズルの後縁線の傾斜角を示す分布線図。
【図６】ノズルの後縁線から噴出する蒸気の流出角を示す分布線図。
【図７】段落を通過する蒸気の流線を示す図。
【図８】ノズルの後縁線から噴出する蒸気の流量を示す分布線図。
【図９】本発明に係る軸流タービンの第１実施例を示し、ノズルの後縁線側から見た概略断面図。
【図１０】本発明に係る第１実施例におけるノズルの形状を示す模式図。
【図１１】従来の軸流タービンの段落の一部を示す概略断面図。
【図１２】図１１のＢ−Ｂ矢視方向から見たノズルの概略断面図。
【図１３】図１２におけるタービン軸の回転中心を通る基準線（ラジアル線）に対するノズルの後縁線の傾斜角を示す分布線図。
【図１４】ノズルから噴出する蒸気の速度三角形を示す図。
【図１５】図１３および図１４に基づく段落を通過する蒸気の流線を示す図。
【図１６】図１５に基づく蒸気の流量を示す分布線図。
【図１７】従来の他の実施例を示す軸流タービンのノズルの後縁線側から見た概略断面図。
【図１８】図１７におけるノズルから噴出する蒸気の流出角を示す分布線図。
【図１９】図１７におけるノズルの形状を示す模式図。
【図２０】図１９におけるタービン軸の回転中心を通る基準線（ラジアル線）に対するノズルの後縁線の傾斜角を示す分布線図。
【図２１】図１８および図２０に基づく段落を通過する蒸気の流線を示す図。
【図２２】図２１に基づく蒸気の流量を示す分布線図。
【図２３】従来のさらに別の実施例を示す軸流タービンのノズルの後縁線側から見た概略断面図。
【図２４】図２３におけるノズルの形状を示す模式図。
【図２５】倒し翼の傾斜角と、湾状曲線を備えたノズルの傾斜角とを比較した傾斜角分布線図。
【図２６】図２５に基づく段落を通過する蒸気の流量を示す図。
【図２７】図２６に基づく蒸気の流量を示す分布線図。
【符号の説明】
１ 段落
２ ノズル
３ 動翼
４ タービン軸
５ ノズル内輪
６ ノズル外輪
７ ノズル内周壁
８ ノズル外周壁
９ 後縁線
１０ 前縁線
１１ 段落
１２ ノズル
１３ 動翼
１４ タービン軸
１５ ノズル内輪
１６ ノズル外輪
１７ ノズル内周壁
１８ ノズル外周壁
１９ 後縁線
２０ 蒸気通路
２１ 前縁線
ＳＬ 直線
ＣＬ 湾状曲線[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an axial flow turbine, and more particularly, to an axial flow turbine that improves the blade efficiency of a nozzle among turbine stages accommodated in an expanded flow path.
[0002]
[Prior art]
In recent years, prime movers in power plants, such as steam turbines, have been divided into high-pressure turbines, medium-pressure turbines, and low-pressure turbines in order to increase output, and the thermal energy of the steam supplied from the steam generator is expanded by each turbine. In order to improve the power generation efficiency, how to increase the expansion work in the stage of each turbine when obtaining the rotational power is an important issue. In particular, low-pressure turbines handle a large amount of steam with relatively low pressure and temperature after expansion work in high-pressure and medium-pressure turbines, and output per stage is high-pressure turbines and medium-pressure turbines regardless of unfavorable steam conditions. Higher than that.
[0003]
Thus, since the role of the low-pressure turbine in the steam turbine is high, the improvement in the output per stage of the low-pressure turbine has an important significance leading to the improvement in the output of the entire turbine.
[0004]
Conventionally, a low-pressure turbine is called an axial flow type, and is provided with a plurality of rows in which the steam flowing along the axial direction of the turbine shaft performs expansion work, and a part of the paragraph has a configuration shown in FIG. It has been adopted.
[0005]
The paragraph 1 includes the nozzle 2 and the moving blade 3 and is provided in a plurality of rows along the axial direction Xa of the turbine shaft 4.
[0006]
The nozzle 2 and the rotor blade 3 constituting one paragraph are both arranged annularly along the circumferential direction with respect to the turbine shaft 4, and the thermal energy of the steam passing between the annular rows is caused to expand by the nozzle 2 and the speed is increased. Instead of energy, the moving blade 3 is rotated by the velocity energy, and rotational power is obtained from the turbine shaft 4 by the rotational force.
[0007]
A nozzle 2 that rotates by applying velocity energy to the rotor blade 3 is fixed at both ends by a ring-shaped nozzle inner ring 5 and a nozzle outer ring 6, and a nozzle width (blade width) from the nozzle inner peripheral wall 7 toward the nozzle outer peripheral wall 8. ) Is gradually expanded toward the downstream moving blade 3 side, and the velocity energy of the steam ejected from the trailing edge line 9 is changed from the nozzle root portion (nozzle inner peripheral wall side) radial position Rr to the nozzle tip portion (nozzle outer peripheral wall side) radius. It is intended to have a uniform distribution up to the position Rt.
[0008]
Further, the nozzle outer peripheral wall 8 at the nozzle tip portion radial position Rt is formed in an expanded flow path having a flare angle, and during the expansion work of the steam in the previous paragraph, the steam specific volume accompanying the decrease in steam pressure and temperature. In response to this increase, the expansion work of the nozzle 2 can be performed more.
[0009]
On the other hand, other examples in which the output per unit of the low-pressure turbine is improved are shown in FIG. 17 and FIG.
[0010]
In the example shown in FIG. 17, the blade shape of the nozzle 2 is made the same as that shown in FIG. 11, while the trailing edge line 9 of the nozzle from the nozzle root portion radial position Rr to the nozzle tip portion radial position Rt is connected to the turbine shaft 4. The radial line Xr (radial line) extending radially from the center point O is crossed. In the example shown in FIG. 23, the trailing edge line 9 of the nozzle 2 is moved from the nozzle root portion radial position Rr to the nozzle. It is formed in a bay-like curve connected by an arc having a certain curvature toward the tip portion radial position Rt.
[0011]
In the former nozzle 2, the leading edge line 10 and the trailing edge line 9 are so-called forwardly moved with respect to the radial line Xr in order to prevent the steam flow from becoming a low flow rate region around the nozzle root portion radial position Rr ( The turbine shaft 4 is rotated in the counter-rotating direction) or backward (the rotating direction of the turbine shaft 4).
[0012]
Further, the latter nozzle 2 has a trailing edge line 9 with respect to the radial line Xr in order to prevent the steam flow from becoming a low flow rate region around the nozzle root portion radial position Rr and the nozzle tip portion radial position Rt. It is a bay-like curve connected by arcs.
[0013]
As described above, the conventional low-pressure turbine extends the advantages of the nozzle 2 itself, complements the drawbacks, improves the blade efficiency, and improves the output around the paragraph.
[0014]
However, in recent axial turbines, it is required to reduce the consumption of fuel energy and increase the power generation efficiency more than before, and as part of this, seek to improve the output per paragraph, especially the nozzle blade efficiency. Has been. In order to improve the blade efficiency of the nozzle more than before, it is necessary that the flow rate distribution of the steam ejected from the trailing edge line of the nozzle is uniform throughout the entire area from the nozzle root radius position to the nozzle tip radius position. is there.
[0015]
[Problems to be solved by the invention]
In the conventional nozzle 2 shown in FIGS. 11 and 12, both the leading edge line 10 and the trailing edge line 9 are so-called straight blades (nozzles) that are substantially parallel to the radial line Xr extending radially from the center point of the turbine shaft 4. Therefore, the periphery of the nozzle root portion radial position Rr extending from the center point O is a low flow rate region in which boundary layer separation is likely to occur, which is one of the bottlenecks for improving blade efficiency.
[0016]
The reason why the vicinity of the nozzle root portion radial position Rr becomes a low flow rate region of steam is considered to be due to the following causes.
[0017]
In general, as shown in FIG. 13, the straight wing-shaped nozzle 2 reduces the steam outlet angle α ejected from the trailing edge line 9 to the angle αr around the nozzle root portion radius position Rr, and the nozzle tip portion radius. The angle αt is increased around the position Rt. That is, the blade shape of the nozzle 2 changes the steam outflow angle from the nozzle root portion radial position Rr to the nozzle tip radial position Rt.
[0018]
The reason why the steam outflow angle α is larger at the nozzle tip radial position Rt than at the nozzle root radial position Rr is based on the following theory.
[0019]
Normally, when the cylinder forms a flow path that does not expand along the axial direction, the peripheral velocity component Vt of the steam is the constant R₁Is given by the following equation according to the vortexless theory (free vortex).
[0020]
[Expression 2]
R × Vt = C₁          ...... (1)
From Equation (1), the smaller the radius R of the cylinder, the larger the circumferential component Vt of the steam.
[0021]
However, the flow rate distribution of the steam ejected from the trailing edge line 9 of the nozzle 2 is desirably uniform over the entire region from the nozzle root portion radial position Rr to the nozzle tip portion radial position Rt in order to increase blade efficiency. . Specifically, it is desirable that the steam axial flow velocity component Va (radial velocity component) is constant. This axial flow velocity component Va is a vector line when the circumferential velocity component Vt of the turbine shaft 4 and the flow velocity V of the steam ejected from the nozzle 2 and the flow angle α thereof, as shown by the velocity triangle in FIG. From the figure, it is geometrically represented by the following equation.
[0022]
[Equation 3]
Va = Vttanα (2)
From the above formulas (1) and (2), the following formula is established as a relational expression between the radius R of the cylinder and the outflow angle α of the steam.
[0023]
[Expression 4]
α = tan^-1(Va / C₁× R) ...... (3)
In the formula (3), (Va / C₁) Is constant from the nozzle root portion radius position Rr to the nozzle tip portion radius position Rt, the steam outflow angle α increases in proportion to the increase in the radius R of the cylinder. In FIG. 14, the Xa coordinate indicates the axial direction of the turbine shaft 4, and the coordinate Xc indicates the circumferential direction of the turbine shaft 4.
[0024]
In this way, as shown in FIG. 13, the straight blade-shaped nozzle 2 increases the steam outflow angle α by increasing the steam outflow angle α from the nozzle root portion radial position value Rr toward the nozzle tip portion radial position Rt. The amount was made uniform.
[0025]
However, in the straight blade-shaped nozzle 2, as described above, the steam outflow angle α is increased from the nozzle root portion radial position Rr toward the nozzle tip portion radial position Rt to achieve uniform distribution of the steam outflow. In practice, however, as shown in FIG. 15, the streamlines S of the steam are relatively biased toward the nozzle outer peripheral wall 8 on the nozzle tip radial position Rt side, and the nozzle inner peripheral wall 7 on the nozzle root radial position Rr side. The surrounding area was in a low flow area. The reason why the periphery of the nozzle inner peripheral wall 7 becomes a low flow rate region is that when the stream line S of the steam passes through the moving blade 3, it is pushed toward the nozzle outer ring 6 by centrifugal force, and this pressing force is applied only to the moving blade 3. It is considered that the streamline S passing through the nozzle 2 is also affected. Further, the nozzle outer peripheral wall 8 on the nozzle tip portion radial position Rt side copes with the specific volume of the steam that is increased by the expansion work in the previous paragraph, and extends from the nozzle root portion radial position Rr to the entire nozzle tip portion radial position Rt. It is formed in an expanded flow path with a flare angle so that it can perform the expansion work equally, but because of the large specific volume of steam, it cannot be along the expanded flow path due to the influence of gravity. The steam flow line S was slightly disturbed, and the steam flow was slightly worse, if not as much as the nozzle inner peripheral wall 7 side.
[0026]
When the flow rate distribution based on the streamline S of the steam passing through the nozzle 2 is shown in FIG. 16, the steam flow rate on the nozzle inner peripheral wall 7 side at the nozzle root portion radial position Rr is extremely low and the nozzle at the nozzle tip portion radial position Rt. The steam flow rate is also slightly reduced on the outer peripheral wall 8 side. In FIG. 16, the coordinate R represents the radial distance (radial line Xr direction distance) of the nozzle 2, and the coordinate Q represents the steam flow rate passing through the nozzle 2.
[0027]
In this way, in the straight blade-shaped nozzle 2, the flow rate of the vapor passing through the entire region from the nozzle root portion radial position Rr to the nozzle tip portion radial position Rt is not uniform, and therefore boundary layer separation occurs from the low flow rate region. As a result, the blade efficiency was not improved.
[0028]
Further, the nozzle 2 shown in FIGS. 17 and 19 has a nozzle root portion radial position Rr and an arbitrary radial position R of the trailing edge line 9 formed in a straight shape from the nozzle inner peripheral wall 7.₀, Inclination angles βr, β at each position of the nozzle tip portion radial position Rt₀, Β_tlThese are so-called trailing blades (nozzles) that are all taken at a positive angle with respect to a reference line (hereinafter referred to as a radial line Xr), but the periphery on the nozzle outer peripheral wall 8 side of the nozzle tip radial position Rt is This is a low flow rate region where boundary layer separation is likely to occur, which has been a drawback in increasing blade efficiency. Note that the inclination angles βr, β₀, Β_tlTook the direction of rotation of the turbine shaft 4 as positive and the direction of anti-rotation as negative.
[0029]
It is considered that the reason why the vicinity of the nozzle inner peripheral wall 7 side of the nozzle tip portion radial position Rt becomes the low flow rate region of the steam is as follows.
[0030]
When the trailing edge line 9 of the nozzle 2 intersects the radial line Xr and is inclined to the plus side (the rotational direction side of the turbine shaft 4), the outflow angle α of the steam ejected from the trailing edge line 9 is shown in FIG. As shown, the angle αr is small around the nozzle root portion radial position Rr, and the angle αt is large around the nozzle tip portion radial position Rt, which is the same as the steam outflow angle distribution diagram shown in FIG. It has become. The steam outflow angle distribution diagrams are the same even if the trailing edge line 9 of the nozzle 2 intersects the radial line Xr, the blade element shape itself is the same, and the inertia principal axis (blade element) of the blade element is the same. This is because the center of the cross-section) has not changed.
[0031]
On the other hand, as shown in FIG. 19, the inclination angle β of the trailing edge line 9 of the nozzle 2 with respect to the radial line Xr is the nozzle root portion radial position Rr and the arbitrary radial position R.₀When looking at each point position of the nozzle tip radius position Rt,
[Equation 5]
βr> β₀> Β_tl> 0 (4)
It is a relational expression. This relational expression can inevitably be obtained from geometrical calculation. When the relation of the above expression is plotted, the inclination angle distribution diagram of the trailing edge line 9 shown in FIG. 20 is obtained.
[0032]
In this way, the trailing edge line 9 of the nozzle 2 is connected to each radial position Rr, R.₀, Rt, tilt angles βr, β satisfying the above relationship₀, Β_tl21, among the stream lines S passing through the paragraph 1, the stream line S on the nozzle inner peripheral wall 7 side of the nozzle root portion radial position Rr of the nozzle 2 is made uniform, but the nozzle The streamline S on the nozzle outer peripheral wall 8 side at the tip portion radial position Rt is a so-called low flow rate region that does not exist. When the steam flow distribution based on the streamline S is graphed, as shown in FIG. 22, the nozzle tip portion radius is higher on the nozzle inner peripheral wall 7 side of the nozzle root portion radius position Rr than on the nozzle inner wall 7 side. The nozzle outer peripheral wall 8 side at the position Rt is extremely small.
[0033]
Considering this cause in detail, the trailing edge line 9 of the nozzle 2 has a radial position Rr, Rr as shown in FIG.₀, Rt is inclined to the plus side (the rotation direction of the turbine shaft 4) with respect to the radial lines Xr, Xr,..., The steam ejected from the trailing edge line 9 is the nozzle inner peripheral wall at the nozzle root radial position Rr. It is considered that a pressing force (vector) toward the 7 side is generated and this pressing force is against the centrifugal force of the rotor blade 3.
[0034]
In this way, in the so-called trailing blade in which the trailing edge line 9 of the nozzle 2 is inclined to the plus side with respect to the radial line Xr, the low flow rate region problem on the nozzle inner peripheral wall 7 side of the nozzle root radial position Rr is solved. Even in this case, the problem of the low flow rate region on the nozzle outer peripheral wall 8 side at the nozzle tip portion radial position Rt remains, which is a cause of impossibility of improving the blade efficiency.
[0035]
Further, the trailing edge line 9 of the nozzle 2 of the bay-shaped curve shown in FIGS. 23 and 24 has an arbitrary radius position R under a certain curvature from the nozzle root portion radial position Rr.₀Curve C towards₁In addition, arbitrary radius position R₀Curve C toward the nozzle tip radial position Rt under a certain curvature from₂The inclination angle βr is added to the radial lines Xr and Xr (in the rotational direction of the turbine shaft 4), and the inclination angle β_tlAre both negative (the counter-rotating direction of the turbine shaft 4). That is, the arbitrary radius position R₀Tilt angle β with respect to radial line Xr₀Is zero, the inclination angle with respect to the radial line Xr at the nozzle root portion radial position Rr is βr> 0, and the inclination angle with respect to the radial line Xr at the nozzle tip portion radial position Rt is β_tc<0.
[0036]
These inclination angles βr, β_tcAnd a nozzle 2 having a bay-like curve, and inclination angles βr, β shown in FIG._tlWhen compared with a tilting wing provided with a radial position Rr, R, as can be understood from FIG.₀, Rt tilt angle βr, R_tl, Β_tcThe absolute value of is smaller for the bay-shaped curved nozzle. In FIG. 25, the coordinate R indicates the radial direction / distance of the radial line Xr extending radially from the center point O of the turbine shaft 4, and the coordinate β indicates the inclination angle value with respect to the radial line Xr.
[0037]
Inclination angle βr, β of nozzle 2 of bay-shaped curve_tcIn both cases, the tilt angles βr, β_tlThe absolute value is smaller than the pressure acting force toward the nozzle inner peripheral wall 7 side of the nozzle root portion radial position Rr of the steam ejected from the trailing edge line 9 of the nozzle 2 and the nozzle tip portion radial position Rt of the steam. It is considered that the pressing force toward the nozzle outer peripheral wall 8 side is relatively high.
[0038]
Under these considerations, when the streamline S of the steam passing through the paragraph 1 is plotted, as shown in FIG. 26, it is small on the nozzle root portion radial position Rr side and also on the nozzle tip portion radial position Rt side. It is dense. Further, when the flow rate distribution of the steam is graphed based on the streamline S of FIG. 26, as shown in FIG. 27, the flow rate is low at the nozzle root radius position Rr side, and the nozzle tip radius A high flow rate Q is obtained on the position Rt side. The high flow rate Q is considered to be due to the influence of the centrifugal force of the rotor blade 3 in addition to the pressing force.
[0039]
As described above, even in the nozzle 2 in which the trailing edge 9 is formed in a bay-like curve, the flow rate balance is accompanied by the poor steam flow between the nozzle root portion radial position Rr side and the nozzle tip portion radial position Rt side. Deviations appear in the blades, which is a cause of impossibility of improving blade efficiency.
[0040]
The present invention has been made in consideration of the above-described circumstances, and the blades are made to optimize the flow rate balance in which the steam passing through the paragraph flows uniformly from the nozzle root portion radial position to the entire nozzle tip portion radial position. An object is to provide an axial turbine having improved efficiency.
[0041]
[Means for Solving the Problems]
  In order to achieve the above object, an axial flow turbine according to the present invention comprises a paragraph in an axial flow row along the axial direction as described in claim 1, and the paragraph is constituted by a nozzle and a moving blade. In an axial flow turbine in which both ends of the nozzle are fixed with a nozzle inner ring and a nozzle outer ring and the nozzle outer ring is extended in the axial direction to form an expanded flow path, the trailing edge line of the nozzle is connected to the nozzle height from the nozzle inner ring. To the middle positionWhile tilting linearly with respect to a reference line passing through the center of rotation of the turbine shaft, this linear tilt is positioned on the rotational direction side of the turbine shaft, while from the nozzle height intermediate position to the nozzle outer ring, a bay shape A curve is formed, and this bay-shaped curve is positioned on the counter-rotating direction side of the turbine shaft, the curvature of the bay-shaped curve is R, and the distance from the rotation center of the turbine shaft to the inner peripheral wall of the nozzle inner ring is Rr When the distance from the rotation center of the turbine shaft to the outer peripheral wall of the nozzle outer ring is Rt,
[Formula 6]
    (Rt-Rr) / 2 <R <10 (Rt-Rr)
Set within the range ofIs.
[0046]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an axial flow turbine according to an embodiment of the present invention will be described with reference to the accompanying drawings.
[0047]
FIG. 1 is a schematic sectional view showing a part of a paragraph in an axial turbine according to the present invention.
[0048]
The paragraph 11 is constituted by the nozzle 12 and the moving blade 13, and a plurality of them are provided in the axial flow row along the axial direction Xa of the turbine shaft 14.
[0049]
Both ends of the nozzle 12 are fixed by a ring-shaped nozzle inner ring 15 and a nozzle outer ring 16, and the nozzle outer ring 16 is engaged and held in a casing (not shown). The nozzle 2 gradually increases the nozzle width (blade width) from the nozzle inner peripheral wall 17 of the nozzle inner ring 15 toward the outer diameter direction (the nozzle longitudinal direction outer side) of the nozzle outer ring 18 of the nozzle outer ring 16, and the trailing edge line 19 The velocity energy of the steam ejected from the nozzle is designed to be uniformly distributed in the radial direction from the nozzle root portion (nozzle inner peripheral wall side) radial position Rr to the nozzle tip portion (nozzle outer peripheral wall side) radial position Rt.
[0050]
In addition, the nozzle outer peripheral wall 18 at the nozzle tip radius position Rt extends along the axial direction Xa, and is formed in an expanded flow path having a flare angle. The expansion work of the nozzle 12 can be increased by coping with the increase in the steam specific volume accompanying the decrease in pressure and temperature.
[0051]
On the other hand, the rotor blades 13 are implanted in the turbine shaft 14 and rotated by the velocity energy of the steam ejected from the nozzles 12 to obtain rotational power (torque) for driving a generator (not shown) from the rotational force. .
[0052]
FIG. 2 is a schematic perspective view of the nozzle 12 as seen from line AA in FIG.
[0053]
The nozzles 12 are annularly arranged along the ring-shaped nozzle inner peripheral wall 17 and the nozzle outer peripheral wall 18 to form a steam passage 20, and the thermal energy of the steam flowing in from the leading edge line 21 is expanded in the steam passage 20. In this case, it is converted into velocity energy, and the velocity energy is applied to the moving blade 13 from the trailing edge line 19.
[0054]
As shown in FIG. 3, the rear edge line 19 of the nozzle 12 is aligned with reference lines (hereinafter referred to as radial lines) Xr, Xr,... Passing through the rotation center O of the turbine shaft 14. A straight line SL extending radially from the root portion radial position Rr and inclined in the rotational direction of the turbine shaft 14 (the circumferential direction of the nozzle inner peripheral wall 17), and the turbine shaft 14 from the middle to the nozzle tip portion radial position Rt of the nozzle outer peripheral wall 18 And a bay-shaped curve CL formed in the counter-rotating direction.
[0055]
The shape of the trailing edge line 19 of the nozzle 12 will be described in detail. As shown in FIG. 4, the straight line SL has an inclination angle βr with respect to the radial line Xr passing through the rotation center O of the turbine shaft 14. P. C. D. Radial position R (which is an abbreviation for pitch circle of diamond and refers to an intermediate position in a region where steam passes through the nozzle 12)_PCDIt is extended radially.
[0056]
On the other hand, the bay-shaped curve CL has the curvature R and the nozzle P.D. C. D radius position R_PCDIs connected to the straight line SL, and the radial position R passes through the rotation center O of the turbine shaft 14.₀With respect to the radial line Xr, the inclination angle is made zero and the nozzle line is extended to the radial position Rt. The nozzle P.I. C. D. Radius position R_PCDThe angle of inclination of the bay-like curve CL at β is β relative to the radial line Xr passing through the rotation center O of the turbine shaft 14._PCDThe inclination angle of the bay-shaped curve CL at the nozzle tip portion radial position Rt is βt with respect to the radial line Xr.
[0057]
The curvature R of the bay-shaped curve CL is set by satisfying the following relational range at the nozzle root portion radial position Rr and the nozzle tip portion radial position Rt.
[0058]
[Expression 7]

[0059]
The range of this relational expression is that the pressure acting force of the steam ejected from the bay-shaped curve CL is slightly saved in consideration of the centrifugal force of the rotor blade 13, and the nozzle tip radial position Rt side has a high flow rate. In order to avoid this, it is an experimental result calculated by repeating trial and error.
[0060]
The above relational expression is the most preferable application range that avoids a high flow rate on the nozzle tip radial position Rt side due to the pressing force of steam.
[0061]
FIG. 5 shows the inclination angle value of the straight line SL and the inclination angle value of the bay-shaped curve CL of the trailing edge line 19 of the nozzle 12 with respect to the radial line Xr passing through the rotation center O of the turbine shaft 14 at the coordinate β. The coordinate R indicates the radial distance value extending radially through the rotation center O of the turbine shaft 14. Moreover, FIG. 6 shows the outflow angle of the steam corresponding to the inclination angle change values of the straight line SL and the bay-like curve CL shown in FIG. The coordinate α indicates the steam outflow angle change value corresponding to the inclination angle change values of the straight line SL and the bay-like curve CL in FIG. 5.
[0062]
5 and 6, the inclination angle β of the straight line SL is determined by the nozzle P.D. C. D. Radius position R_PCDFurther, the steam outflow angle α decreases from the nozzle root radial position Rr to the nozzle P.D. C. D. Radius position R_PCDFrom these data, the pressing force of the steam ejected on the straight line SL of the trailing edge line 19 is determined from the nozzle root portion radial position Rr side to the nozzle P.P. C. D. Radius position R_PCDThe direction is changing as he goes to the side. Therefore, the pressure acting force of the steam ejected from the straight line SL of the trailing edge line 19 also acts on the nozzle root part radial position Rr side, so that the steam flows to the nozzle root part radial position Rr, and the low pressure around the nozzle root part radial position Rr. A flow range can be avoided.
[0063]
On the other hand, as shown in FIGS. C. D. Radius position R_PCDWhile the inclination angle β is sharply decreased from the nozzle tip portion radial position Rt to the nozzle tip portion radial position Rt, the absolute value of the inclination angle βt of the nozzle tip portion radial position Rt is smaller than the inclination angle βr of the nozzle root portion radial position Rr. The change value of the outflow angle α of the steam corresponding to the change value of the inclination angle β is also the nozzle P.P. C. D. Radius position R_PCDTo the nozzle tip radius position R within the range of the nozzle tip radius position Rt₀A peak value is taken at a zero inclination angle with respect to the radial line Xr at, and thereafter, the outflow angle αt is lowered at the nozzle tip radial position Rt.
[0064]
  As can be understood from the above-mentioned data, the pressure acting force of the steam ejected from the bay-shaped curve CL is the nozzle radius position R.₀It has become the maximum.Nozzle radius position R ₀ soThe reason why the pressing force is maximized is to prevent the nozzle tip radial position Rt from becoming a high flow rate region due to the centrifugal force of the moving blade 13.
[0065]
FIG. 7 plots the streamline S of the steam passing through the paragraph 11 based on the change value of the inclination angle β and the change value of the steam outlet angle α of the straight line SL and the bay-like curve CL shown in FIGS. 5 and 6. FIG. 8 shows the distribution of the steam flow rate Q from the nozzle root portion radial position Rr to the nozzle tip portion radial position Rt based on the streamline S of FIG.
[0066]
As can be understood from FIGS. 7 and 8, when the vapor is ejected from the trailing edge line 19 of the nozzle 12, the vapor is uniform over the entire region from the nozzle root portion radial position Rr to the nozzle tip portion radial position Rt.
[0067]
Thus, in the axial turbine according to the present invention, the trailing edge line 19 of the nozzle 12 is divided into an inclined straight line and a bay-shaped curve, and a pressing force is applied to the nozzle root radial position Rr. A low flow rate region on the nozzle root portion radial position Rr side can be avoided. Further, since the pressing force applied to the nozzle tip radius position Rt is saved, a high flow rate region on the nozzle tip radius position Rt side can be avoided.
[0068]
9 and 10 are schematic views showing a first embodiment of the axial turbine according to the present invention. The same components as those in FIGS. 2 and 3 are denoted by the same reference numerals.
[0069]
As shown in FIG. 9, the present embodiment is basically the same as the embodiment shown in FIGS. 2 and 3 in that the rear edge line 19 of the nozzle 12 is divided into a straight line SL and a bay-like curve CL. However, the shape of the bay-shaped curve CL is different.
[0070]
As shown in FIG. 10, the bay-shaped curve CL has an inclination angle βr with respect to the radial line Xr passing through the rotation center O of the turbine shaft 14, and the nozzle P.D. C. D. Radius position R_PCDIs connected to a straight line SL extending radially toward the surface, and the curvature thereof is a deformed oval curvature. The curvature of the deformed oval is the nozzle radius position R₀Thus, the inclination angle is set to zero with respect to the radial line Xr, and the nozzle tip radius position Rt is set in a range where a high flow rate region can be avoided.
[0071]
Thus, the present embodiment avoids the rear edge line 19 of the nozzle 12 from becoming the low flow rate region on the nozzle root portion radial position Rr side, and the nozzle tip portion radial position Rt side from becoming the high flow rate region. Since the straight line SL to avoid and the bay-shaped curve CL are divided, the flow rate distribution of the steam ejected from the trailing edge line 19 of the nozzle 12 is made uniform as in the embodiment shown in FIGS. be able to.
[0072]
【The invention's effect】
As described above, in the axial flow turbine according to the present invention, the nozzle trailing edge line is connected to the nozzle P.D. C. D is formed in an inclined straight line across the radial position, and the nozzle P.D. C. D. Since the bay-like curve is formed from the radial position to the nozzle tip portion radial position, the steam can flow at an appropriate flow rate on both the nozzle root portion radial position side and the nozzle tip portion radial position side.
[0073]
In the axial turbine according to the present invention, the curvature of the bay-shaped curve is set in the range of (Rt−Rr) / 2 <R <10 (Rt−Rr). C. D. A uniform vapor flow rate can flow from the radial position side to the nozzle tip portion radial position side.
[0074]
In addition, the axial turbine according to the present invention provides the peak value of the pressing force of the steam ejected from the bay-shaped curve as the nozzle P.P. C. D. Since it is set within the range from the radial position to the nozzle tip portion radial position, it is possible to allow steam to flow to the nozzle tip portion radial position side as an appropriate flow rate even under the influence of the centrifugal force of the moving blade.
[0075]
Therefore, in the axial turbine according to the present invention, the flow rate distribution of the steam ejected from the trailing edge line of the nozzle can be made uniform over the entire region from the nozzle root portion radial position to the nozzle tip portion radial position, and the nozzle having high blade efficiency. The power generation efficiency can be dramatically improved by improving the blade efficiency of the axial turbine.
[Brief description of the drawings]
FIG. 1 is a schematic sectional view showing a part of a stage of an axial-flow turbine according to the present invention.
2 is a schematic perspective view of the nozzle as viewed from the direction of arrows AA in FIG.
FIG. 3 is a schematic cross-sectional view of the axial turbine according to the present invention as seen from the trailing edge side of the nozzle.
FIG. 4 is a schematic diagram showing the shape of a nozzle according to the present invention.
FIG. 5 is a distribution diagram showing an inclination angle of a trailing edge line of a nozzle with respect to a reference line (radial line) passing through the rotation center of the turbine shaft.
FIG. 6 is a distribution diagram showing an outflow angle of steam ejected from the trailing edge line of the nozzle.
FIG. 7 is a diagram showing a streamline of steam passing through a paragraph.
FIG. 8 is a distribution diagram showing the flow rate of steam ejected from the trailing edge line of the nozzle.
FIG. 9 is a schematic sectional view showing the first embodiment of the axial turbine according to the present invention, viewed from the trailing edge line side of the nozzle.
FIG. 10 is a schematic diagram showing the shape of a nozzle in the first embodiment according to the present invention.
FIG. 11 is a schematic cross-sectional view showing a part of a paragraph of a conventional axial flow turbine.
12 is a schematic cross-sectional view of the nozzle as seen from the direction of arrows BB in FIG.
13 is a distribution diagram showing the inclination angle of the trailing edge line of the nozzle with respect to a reference line (radial line) passing through the rotation center of the turbine shaft in FIG. 12;
FIG. 14 is a diagram showing a velocity triangle of steam ejected from a nozzle.
FIG. 15 shows a streamline of steam passing through a paragraph based on FIGS. 13 and 14.
FIG. 16 is a distribution diagram showing the flow rate of steam based on FIG.
FIG. 17 is a schematic cross-sectional view seen from the trailing edge side of a nozzle of an axial flow turbine showing another conventional example.
18 is a distribution diagram showing an outflow angle of steam ejected from the nozzle in FIG. 17;
19 is a schematic diagram showing the shape of the nozzle in FIG.
20 is a distribution diagram showing an inclination angle of a trailing edge line of a nozzle with respect to a reference line (radial line) passing through the rotation center of the turbine shaft in FIG. 19;
FIG. 21 is a diagram showing streamlines of steam passing through the paragraphs based on FIGS. 18 and 20;
22 is a distribution diagram showing the flow rate of steam based on FIG. 21. FIG.
FIG. 23 is a schematic cross-sectional view of an axial flow turbine nozzle as seen from the trailing edge side of a conventional example.
24 is a schematic diagram showing the shape of the nozzle in FIG. 23. FIG.
FIG. 25 is an inclination angle distribution diagram comparing the inclination angle of the wing blade and the inclination angle of the nozzle having a bay-like curve.
26 shows the flow rate of steam passing through the paragraph based on FIG. 25. FIG.
FIG. 27 is a distribution diagram showing the flow rate of steam based on FIG.
[Explanation of symbols]
1 paragraph
2 nozzles
3 blades
4 Turbine shaft
5 Nozzle inner ring
6 Nozzle outer ring
7 Nozzle inner wall
8 Nozzle outer wall
9 Trailing edge line
10 Leading edge line
11 paragraph
12 nozzles
13 Moving blade
14 Turbine shaft
15 Nozzle inner ring
16 Nozzle outer ring
17 Nozzle inner wall
18 Nozzle outer peripheral wall
19 Trailing line
20 Steam passage
21 Leading edge line
SL straight line
CL Bay curve

Claims (1)

Along the axial direction, there is a paragraph in the axial flow line, and the paragraph is composed of a nozzle and a moving blade. Both ends of the nozzle are fixed with a nozzle inner ring and a nozzle outer ring, and the nozzle outer ring is extended in the axial direction to expand. In the axial flow turbine formed in the flow path, the trailing edge line of the nozzle is inclined linearly from a nozzle inner ring to a nozzle height intermediate position with respect to a reference line passing through the rotation center of the turbine shaft. Is formed on the turbine shaft rotation direction side, while the nozzle height intermediate position to the nozzle outer ring are formed in a bay-shaped curve, and the bay-shaped curve is positioned on the turbine shaft counter-rotation direction side. In addition, the curvature of the bay-shaped curve is R, the distance from the rotation center of the turbine shaft to the inner peripheral wall of the nozzle inner ring is Rr, and the distance from the rotation center of the turbine shaft to the outer peripheral wall of the nozzle outer ring When the Rt, the curvature R,

An axial turbine characterized by being set within the range of

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